Applications in which the presence of an object in the vicinity of another object shall be determined, are numerous. For example, devices comprising transmitters to wirelessly transmit data signals using a wireless LAN standard or a mobile telecommunication standard, such as for example one of the releases of the mobile telecommunication standard, namely, the long-term evolution (LTE) standard, may require to decrease a power of the transmission signal when human tissue is in the vicinity of the transmit antennas. The Federal Communications Commission (FCC) and the European Telecommunications Standards Institute (ETSI) provide regulations for a maximum acceptable radiation intensity for human tissue. For example, a maximum specific absorption rate (SAR, W/kg) is not permitted to exceed. The SAR depends on the proximity of the tissue to the antennas used to radiate the signal and amount and form of the transmitted power. In order to be compliant with the provisions, several test cases have to be met. For example, the SAR must not exceed a predetermined threshold when human tissue or a measurement body having similar characteristics (an SAR phantom) is in direct contact with the investigated device at arbitrary locations thereof. In order to determine proximity of an object or, for example, human tissue to a device, capacitive sensors may be used. However, when proximity of an object to, for example, all six edges of a rectangular device is to be monitored, numerous sensors may be required, for example for tablet computers or mobile phones, amounting to considerable costs for the proximity detection. In the event of a determined proximity of an object or human tissue, the transmit power of a wireless communication device or of a transmitter within the device under investigation needs be reduced in order to meet the SAR requirements.
There may be a desire to provide for the possibility to determine proximity in a more efficient manner.